1. Field of the Invention
The invention relates to a process for forming a waterproof keyboard. More specifically, the present invention relates to a process for forming a printed circuit film used in a waterproof keyboard.
2. Description of the Related Art
Notebooks have become widely used as portable computers. The different types of notebook include ultra thin type notebooks and all-in-one type notebooks. The notebook essentially consists of an input device, a monitor and a host. The input device is a human interface device (HID), such as mouse, keyboard, and writing/voice identification system. Most of the application programs are operated via the input device. In order to be more user-friendly, the current notebook is further designed more lightweight and more compact.
Additionally, the waterproof characteristic of the input device is also important, because it may extend the service life of the notebook. Within the keyboard of a conventional notebook, a waterproof coating is usually applied to a printed circuit film of the keyboard to protect circuits thereof from contacting with external moisture, water or liquid.
FIG. 1 is a schematic view showing a conventional process for manufacturing the printed circuit film of a waterproof keyboard. With reference to FIG. 1, the process includes a step S100 of forming a circuit layer, a step S102 of forming an insulation layer, a step S104 of applying a waterproof coating, a step S106 of laminating the insulation layer with the circuit layer, a step S108 of curing and a step S110 of punching.
At step S100, a circuit layer is formed via printing conductive patterns on a PET film. The conductive patterns include a plurality of circuits and contacts. At step S102, the insulation layer is formed via punching a PET film to form a plurality of openings respectively corresponding to the contacts of the circuit layer.
The waterproof coating is applied over the circuit layer or the insulation layer. The location of the waterproof coating corresponds to that of a positioning hole which is formed after the waterproof coating. Usually, the area of the waterproof coating is larger than a diameter of the positioning hole.
At step S106, the insulation layer is laminated with the circuit layer. FIG. 2 is a schematic view showing the conventional printed circuit film obtained by laminating the circuit layer on the insulation layer. With reference to FIG. 2, a circuit layer 200 is folded into a first circuit portion 200a and a second circuit portion 200b. An insulation layer 300 is interleaved between the first circuit portion 200a and the second circuit portion 200b. Then, the insulation layer is laminated with the circuit layer.
With reference to FIG. 2, the first circuit portion 200a and the second circuit portion 200b of the circuit layer 200 have layouts corresponding to each other. On the first circuit portion 200a are formed a plurality of contacts 202a that respectively correspond to the keys of the keyboard, and a plurality of circuits 204a that respectively electrically connect the contacts 202a. On the second circuit portion 200b are formed a plurality of contacts 202b respectively corresponding to the contacts 202a, and a plurality of circuits 204b respectively corresponding to the contacts 202b. The insulation layer 300 has a plurality of openings 302 that respectively correspond to the contacts 202a and 202b. 
After the insulation layer 300 is laminated with the circuit layer 200, the contacts 202a and 202b are located inside the opening 302 of the insulation layer 200. When a key of the keyboard and the first circuit portion 200a are pressed down, the contact 202a on the first circuit portion 200a is electrically connected to the contact 202b on the second circuit portion 200b, thereby achieving information input.
With reference to FIG. 1, after step S106 where the insulation layer is laminated with the circuit layer, the waterproof coating is cured in step S108. Infrared ray radiation is usually used to cure the waterproof coating. Finally, the cured layers including the first circuit portion 200a, the insulation layer 300 and the second circuit portion 200b are punched to form a plurality of positioning holes that have locations and sizes respectively corresponding to a positioning mechanism of the keyboard.
FIGS. 3A to 3D are schematic views showing how a conventional circuit layer is formed. With reference to FIG. 3A, a circuit layer is provided. The circuit layer has a first circuit portion 200a and a second circuit portion 200b. The first portion 200a has a plurality of contacts 202a and a plurality of circuits (not shown) thereon. The second circuit portion 200b has a contact 202b and circuit (not shown) thereon. The insulation layer 300 includes a plurality of openings 302. A waterproof coating 400 is applied over a predetermined area of the insulation layer 300 where the first circuit portion 200a, the insulation layer 300, and the second portion 200b are positioned such that the contacts 202a and 202b are thereby located inside the opening 302.
With reference to FIG. 3A, after the waterproof coating is applied, the first circuit portion 200a is laminated with insulation layer 300 and second circuit portion 200b to form a multi-layered film. The contacts 202a and 202b are located inside the openings 302.
With reference to FIG. 3C, after the lamination process, the waterproof coating between the first and second circuit portions is cured by IR. Thereby, a waterproof property is achieved.
With reference to FIG. 3D, after the step S108 of curing, a punching process is performed to form a plurality of positioning holes 402. The area where the waterproof coating is applied corresponds to and covers the locations of the positioning holes 402. Therefore, the waterproof coating 400 prevents moisture, water or liquid from penetrating into the multi-layered film through sidewalls of the positioning holes 402.
FIG. 4 is a schematic view showing the positioning holes and the waterproof coating of the conventional printed circuit film. As shown, the waterproof coating 400 is not completely removed after the punching process is performed to form the positioning holes 402. FIG. 3D is cross-sectional view taken along line I—I of FIG. 4.
In the conventional process for manufacturing the printed circuit film in a waterproof keyboard, the waterproof coating is applied between the circuit layer and the insulation layer. After the lamination process, the distribution of the waterproof coating therefore is not easily controlled. Moreover, the waterproof coating has to be cured by irradiating with IR after the lamination.